The present invention relates to a ratchet wrench and, more particularly, to a ratchet wrench providing sensitive, accurate driving direction-switching operation and reliable positioning effect while prolonging the service life of the ratchet wrench.
U.S. Pat. No. 7,278,339 discloses a reversible ratchet wrench including a head rotatably receiving a drive member. A pawl is slideably received in the head between two positions and releasably engages with the drive member. A ring is mounted around an end of the drive member and includes a tip piece having a slot. A reversing plate is pivotably mounted to the end of the drive member and operatively connected to the ring to turn therewith. A switching member is pivotably received in a receiving hole of the head and includes a protrusion engaged in the slot of the tip piece of the ring such that the switching member is pivoted when the ring is pivoted. The switching member includes a receptacle receiving an elastic element and a pressing member biased by the elastic element to press against the pawl. The reversing plate is pivotable between two operative positions to move the pawl between the two positions to switch the driving direction of the ratchet wrench. However, friction between the ring and the reversing plate causes wear and generates scraps between the ring and the reversing plate. Furthermore, a positioning structure including a pin and a pin hole is required for positioning the reversing plate, leading to an increase in the manufacturing costs as well as adverse affect in the positioning effect due to accumulation of dust in the gaps between the positioning elements. Further, there are many elements between the reversing plate and the switching member with each element having its own play, leading to insensitive driving direction-switching operation. Further, a user may work with his or her head facing upward in some cases. Direction-switching operation may be a problem in these cases when a socket or an extension is coupled to a drive column of the drive member that faces upward, because gravitational force is imparted to the drive member from the socket, the extension or even the object to be the rotated by the ratchet wrench. The user has to remove the socket or extension from the drive column, flips the drive member so that the drive column faces downward, switches the driving direction, and reattaches the socket or extension to the drive column, which is extremely inconvenient and inefficient.
Thus, a need exists for a ratchet wrench providing sensitive, accurate driving direction-switching operation and reliable positioning effect as well as prolonging the service life of the ratchet wrench.